1. Field of the Invention
This invention relates generally to a corona igniter for emitting a radio frequency electric field to ionize a fuel-air mixture and provide a corona discharge, a corona discharge ignition system, and methods of manufacturing the same.
2. Related Art
A corona igniter of a corona discharge ignition system receives a voltage from a power source and emits an electrical field that forms a corona to ionize a mixture of fuel and air of an internal combustion engine. The igniter includes an electrode extending longitudinally form an electrode terminal end to an electrode firing end. An insulator is disposed along the center electrode, and a shell is disposed along the insulator.
The electrode terminal end receives the voltage from the power source and the electrode firing end emits the electrical field that forms the corona. The electrode of the corona igniter may also include a crown at the firing end for emitting the electrical field. The electrical field includes at least one streamer, and typically a plurality of streamers forming the corona. The mixture of air and fuel is ignited along the entire length of the high electrical field generated from the electrode firing end. An example of a corona igniter is disclosed in U.S. Patent Application Publication No. US 2010/0083942 to Lykowski et al.
In an ideal corona ignition system, the corrosion and/or erosion of the metallic parts of the corona igniter in the combustion chamber is low since a corona discharge does not have the high current and high temperatures associated with the discharge of a conventional spark. Although the corona igniter does not include any grounded electrode element in close proximity to the firing tips of the crown, in some applications, there are grounded engine components that come close to the firing tips. Accordingly, it is not always possible to avoid an arc formation, also referred to as arcing, between the corona igniter and grounded component. If an arc forms, the high current and temperatures associated with the arc formation could cause some erosion and/or corrosion damage to the firing tips of the crown. Overtime, the erosion and/or corrosion damage could decrease the quality of corona formation and combustion.